Sometimes it helps to get your chinchilla a "friend" for this purpose. Go to the pet store and buy a stuffed animal that is safe for pets that is about the same size as your chinchilla. Try to stay away from the really fluffy ones since your chin will probably groom his new friend and you don't want him ingesting long hairs. Also, you might have your wife wash her hands before handing him, and change your hand soap. Hopefully a new smell will help discourage him.